# ENTROPY PRODUCTION IN COLLISIONLESS SYSTEMS. III. RESULTS FROM SIMULATIONS

## Abstract

The equilibria formed by the self-gravitating, collisionless collapse of simple initial conditions have been investigated for decades. We present the results of our attempts to describe the equilibria formed in N-body simulations using thermodynamically motivated models. Previous work has suggested that it is possible to define distribution functions for such systems that describe maximum entropy states. These distribution functions are used to create radial density and velocity distributions for comparison to those from simulations. A wide variety of N-body code conditions are used to reduce the chance that results are biased by numerical issues. We find that a subset of initial conditions studied lead to equilibria that can be accurately described by these models, and that direct calculation of the entropy shows maximum values being achieved.

- Authors:

- Department of Physics, University of Wisconsin—La Crosse, La Crosse, WI 54601 (United States)

- Publication Date:

- OSTI Identifier:
- 22522401

- Resource Type:
- Journal Article

- Journal Name:
- Astrophysical Journal

- Additional Journal Information:
- Journal Volume: 805; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPARATIVE EVALUATIONS; DENSITY; DISTRIBUTION FUNCTIONS; ENTROPY; EQUILIBRIUM; GALAXIES; STAR EVOLUTION; VELOCITY

### Citation Formats

```
Barnes, Eric I., and Egerer, Colin P., E-mail: barnes.eric@uwlax.edu, E-mail: egerer.coli@uwlax.edu.
```*ENTROPY PRODUCTION IN COLLISIONLESS SYSTEMS. III. RESULTS FROM SIMULATIONS*. United States: N. p., 2015.
Web. doi:10.1088/0004-637X/805/1/66.

```
Barnes, Eric I., & Egerer, Colin P., E-mail: barnes.eric@uwlax.edu, E-mail: egerer.coli@uwlax.edu.
```*ENTROPY PRODUCTION IN COLLISIONLESS SYSTEMS. III. RESULTS FROM SIMULATIONS*. United States. doi:10.1088/0004-637X/805/1/66.

```
Barnes, Eric I., and Egerer, Colin P., E-mail: barnes.eric@uwlax.edu, E-mail: egerer.coli@uwlax.edu. Wed .
"ENTROPY PRODUCTION IN COLLISIONLESS SYSTEMS. III. RESULTS FROM SIMULATIONS". United States. doi:10.1088/0004-637X/805/1/66.
```

```
@article{osti_22522401,
```

title = {ENTROPY PRODUCTION IN COLLISIONLESS SYSTEMS. III. RESULTS FROM SIMULATIONS},

author = {Barnes, Eric I. and Egerer, Colin P., E-mail: barnes.eric@uwlax.edu, E-mail: egerer.coli@uwlax.edu},

abstractNote = {The equilibria formed by the self-gravitating, collisionless collapse of simple initial conditions have been investigated for decades. We present the results of our attempts to describe the equilibria formed in N-body simulations using thermodynamically motivated models. Previous work has suggested that it is possible to define distribution functions for such systems that describe maximum entropy states. These distribution functions are used to create radial density and velocity distributions for comparison to those from simulations. A wide variety of N-body code conditions are used to reduce the chance that results are biased by numerical issues. We find that a subset of initial conditions studied lead to equilibria that can be accurately described by these models, and that direct calculation of the entropy shows maximum values being achieved.},

doi = {10.1088/0004-637X/805/1/66},

journal = {Astrophysical Journal},

issn = {0004-637X},

number = 1,

volume = 805,

place = {United States},

year = {2015},

month = {5}

}